Networked devices communicate using signals sent over common physical media networks, which can be either wired or wireless. Such a network interconnects devices of different generations having different communication parameters. Backward compatibility of new generation devices with older generation devices, is a desired quality. Compatibility implies co-existence, such that new generation devices do not interfere with old generation transmissions. Compatibility may further imply interoperability, such that new generation devices and old generation devices, are able to communicate there between.
Such devices may be connected in a point-to-point architecture, wherein only two such devices are connected, or in a networked architecture, wherein a plurality of devices share the same physical communication medium and intercommunicate there between.
Conventional communication standards employ several methods in order to ensure backward compatibility. One type of such methods is called “Fall-back”. “Fall-back” methods artificially degrade the capabilities of the later generation device, forcing them to be comparable with those of prior generation devices. A network which is composed of both prior and later generation devices, operates according to the communication standard of the prior generation devices, even for communication between two later generation devices.
Another type of such methods is called self-describing frame format methods. In these methods, when two later generation devices communicate, later generation data formatted transmission is encapsulated, such that the header of the transmission is in prior generation format. The header can include information related to the generation of the data encapsulated thereafter or information related to a destination node. A prior generation device, receiving such data, after decoding the header portion of the data, shall determine that this data is not intended therefor and hence shall ignore the rest of the data. A later generation device, receiving the same transmission, after decoding the header, will decode the rest of the data, using the newer communication standards.
A further method of providing backwards compatibility, is by adding a component, to each prior generation device, which will provide translation capabilities, of later generation standards, to those recognizable by the prior generation device, and vice versa. Such devices allow communication across the network to be conducted, using later generation technology, while allowing prior generation devices, to participate in the data exchange across the network.
U.S. Pat. No. 6,298,051, entitled “High-data-rate supplemental channel for CDMA telecommunications system”, issued to Odenwalder et al., is directed to a method for transmitting a supplemental high rate data channel in tandem with existing data channels over a CDMA over-the-air transmission. This is accomplished by providing a quadrature-phase channel, orthogonal to the in-phase channels used to transmit normal-rate CDMA data, in such a way as to avoid interfering with the in-phase channel. Thus, normal rate capable CDMA devices, which are unable to detect the quadrature-phase channel, are not influenced by the high rate data. The method thus illustrated ensures compatibility of the high-rate capable devices with the normal rate devices.
U.S. Pat. No. 6,011,807, entitled “Method and apparatus for transmitting data in a high rate, multiplexed data communication system”, issued to Castagna et al., is directed to a method and apparatus for determining synchronization and loss of synchronization in a high rate multiplexed data system. The method employs a backwards compatibility flag that allows the apparatus to operate with older systems. By using the backwards compatibility flag to detect if an incoming transmission is initiated in an older system, and activating relevant circuitry accordingly, the apparatus is able to maintain compatibility with older systems.
U.S. Pat. No. 5,987,068, entitled “Method and apparatus for enhanced communication capability while maintaining standard channel modulation compatibility”, issued to Cassia et al., is directed to a method for enhancing communication capabilities. The method modulates a first communication signal, using a standard modulation technique, onto a carrier signal, thereby producing a first transmission signal. The method further modulates a supplemental communication signal onto the first transmission signal, thereby producing a combined transmission signal, which is then broadcast. The standard modulation scheme for the first communication signal, is differential quadrature phase shift keying (DQPSK). When the combined transmission signal is demodulated using DQPSK, the first communication signal is extracted there from. When a receiving device is aware of the enhanced modulation scheme used in the combined transmission signal, it demodulates the signal accordingly, extracting both the first communication signal, and the supplemental communication signal. When a receiving device is not aware of the enhanced modulation scheme it demodulated the combined transmission signal using DQPSK demodulation, extracting the first communication signal. Thus compatibility is ensured when transmitting to a device unaware of the enhanced modulation scheme used.
IEEE Standard 802.3 details the standards for the Ethernet local networking interface and protocol. The 802.3 standard encompasses technologies of various communication rates, namely 10 Mbps, 100 Mbps and 1000 Mbps. In order to ensure backwards compatibility between newer high-rate devices and older low-rate devices, the standard details an auto-negotiation implementation. Accordingly, high-rate devices detect a transmission from a low-rate device, infer a connection to such a device, and reduce the communication rate accordingly. Such a rate reduction ensures backward compatibility with the low-rate communication device.
A family of communication specifications which exhibit backward compatibility, is known as Home Phoneline Networking Alliance (HPNA). The first generation, HPNA-1, defines transmission around a carrier frequency FHPNA-1, with Pulse Position Modulation.
The second generation defines transmission around a carrier frequency FHPNA-2, but with Frequency Diverse/Quadrature Amplitude Modulation (FDQAM/QAM). An HPNA-2 device which communicates with an HPNA-1 device, transmits an HPNA-1 format pulsed transmission around FHPNA-1 using an HPNA-1 transmitter incorporated into the HPNA-2 device. In the presence of HPNA-1 devices, an HPNA-2 device which communicates with a non-HPNA-1 device, commences a transmission with an HPNA-1 format pulsed like header, encapsulating information which causes HPNA-1 devices to discard the rest of the transmission.
U.S. patent application Ser. No. 2002/0015404, entitled “Extended Bandwidth HomePNA System Compatible with HomePNA 2.0”, by Fisher et al., is directed to a method for using an extended bandwidth HPNA system, compatible with the HPNA 2.0 standard, in such a way as to cause HPNA 2.0 systems to ignore transmissions not intended for those systems. The system uses a transmission signal centered on 10 MHz, having a 12 MHz bandwidth, to communicate between extended bandwidth systems. In order to allow for compatibility with HPNA 2.0 systems, the proposed system produces a training sequence that an HPNA 2.0 system is able to train on and determine that the incoming packet is not intended for the HPNA 2.0 receiver. The training sequence is produced by zero padding a 2 MBaud symbol sequence to an 8 MBaud sequence (up-sampling the signal), and then modulating the 8 MBaud sequence on to a 1 MHz carrier. This modulation shift the spectrum of the 8 MBaud sequence by 1 MHz. The shifted signal is then modulated on the 10 MHz carrier. The portion of the modulated signal between 4 MHz and 10 MHz is identical to an HPNA 2.0 signal, thus allowing an HPNA 2.0 receiver to train on the training sequence.